1. Field of the Invention
This invention relates to snowboards and, more particularly, is directed to a snowboard designed with the goal of carving an ideal or xe2x80x9cperfectxe2x80x9d turn during use.
2. Description of Related Art
This portion of the specification is divided for ease in understanding into the following 3 sections:
A. The Deficiencies of Conventional Snowboard Design
B. The Prior Art
C. General Snowboard Structure
A. The Deficiencies of Conventional Snowboard Design
In order to initiate a turn (also called xe2x80x9ccarvingxe2x80x9d a turn), a skier or snowboarder applies pressure to the ski or snowboard in a manner that rotates the ski or snowboard about its longitudinal axis, tilting the ski or snowboard up onto one of its edges (often called the xe2x80x9criding edgexe2x80x9d) and deflecting the ski or snowboard away from the skier or snowboarder. Ideally, the riding edge of the ski or snowboard will create a single slender cut into the snow as the skier or snowboarder carves the turn (called an xe2x80x9cideal turnxe2x80x9d). This type of turn is desirable because it minimizes the friction or drag on the ski or snowboard as it moves through the turn. In addition, this type of turn is the easiest to control. However, as will be fully explained below, this type of turn has been impossible to achieve with conventional snowboard design.
Snowboards were initially manufactured by ski manufacturers, and most of the initial designers of snowboards were therefore ski designers who understandably borrowed heavily from the accepted wisdom of the ski industry. As a consequence, there are many similarities today between skis and snowboards. For example, both skis and snowboards use essentially the same materials, e.g., fiberglass ultra high molecular weight polyethylenes, either singly or in laminated combinations with wood cores, steel edges, and plastic tops and sidewalls. Also, ski construction, e.g., sidewall, sandwich or capped construction, and techniques of manufacture, e.g., presses, composites and laminating, were transferred virtually unchanged to snowboards.
Of importance to the present invention is the way in which skis, and therefore conventional snowboards, flex longitudinally when in use. Trimble et al. (U.S. Pat. No. 5,413,371) disclose that conventional skis form a xe2x80x9cU-shapedxe2x80x9d curve when in use. A skier using a ski that forms a U-shaped curve when in use will be able to carve a turn that approaches an ideal turn without a great deal of difficulty. This is primarily because only one of the skier""s feet is positioned on each ski, thereby applying a single, centrally positioned load onto each ski.
In addition, nearly all skis (and therefore conventional snowboards) include a single camber. As a result, when under little or no downward loading, skis rest on two riding areas, one near the nose of the ski and one near the tail of the ski; the portion of the riding edge between these two riding areas does not contact the snow. When making a turn under rider-induced loading, the entire riding edge is conventionally designed to make contact with the snow. See, e.g., John G. Howe, Skiing Mechanics 108-110 (1ST ed. 1983). This has traditionally been accomplished by using side cuts.
Under conventional ski design principles, the relative stiffness of each portion of the ski along its length is considered to be of little importance to its turning characteristics. Significantly, conventional ski design fails to account for the longitudinal shape of the ski when downward loading increases beyond the point at which the riding edge of the ski fully contacts the snow. In other words, conventional ski design focuses simply on ensuring that the riding edge fully contacts the snow, thereby ignoring how the ski bends during turns. In reality, a ski does not stop downwardly flexing once the riding edge makes contact with the snow surface. Under ordinary conditions, the ski continues to flex, both displacing and compressing the snow and forming a downwardly arched curve.
Merely designing a snowboard or ski so that its riding edge fully contacts the snow during turns, while ignoring the shape the board or ski bends into beyond the point at which the riding edge fully contacts the snow, results in poor turning performance, especially in sharp, tight turns.
In fact, it is nearly impossible for a snowboarder to carve an ideal turn on a conventionally designed snowboard (a snowboarder is carving an ideal turn, or is at least approaching an ideal turn, when the back portion of the snowboard follows substantially the same track as the front portion of the board).
Several factors contribute to the poor turning performance of conventional snowboards. First, in contrast to a skier, both of the snowboarder""s feet are positioned on the snowboard. Thus the snowboarder applies two non-centrally located loads onto the snowboard during a turn. The application of two non-centrally located loads to a conventional snowboard (which is typically stiffest in its center section) results in a large flattened area in the center section of the snowboard. Consequently, it is very common for the back half of the snowboard to cut its own path through the snow during a turn (sometimes called xe2x80x9cplowingxe2x80x9d), rather than tracking the path made by the front half. Plowing is most pronounced during sharp turns and is undesirable because it makes the snowboard more difficult to control in turns and greatly increases the friction or drag on the snowboard as it moves through the snow.
Use of side cuts improves the flexibility of the central portion of a snowboard slightly, but far from overcomes the deficiencies of conventional snowboards. In addition, most prior art snowboards have a single camber. As explained in my prior U.S. Pat. No. 5,823,562, a snowboard having a single camber is difficult to control regardless of the longitudinal flexibility of the snowboard.
Finally, to design a snowboard merely so that its riding edge makes full contact with the surface when turning fails to take into account subsequent flexing of the snowboard.
B. Third Prior Art
Representative of the prior art snowboards are Remondet, U.S. Pat. No. 5,018,760, Carpenter et al., U.S. Pat. No. 5,261,689, Nyman, U.S. Pat. No. 5,462,304, and Deville et al., U.S. Pat. No. 5,573,264.
Remondet shows (FIG. 4) a snowboard having a thickness that is at a maximum in the center of the snowboard, gradually diminishes towards the tail and nose portions of the snowboard. Thus, the center section is the stiffest portion of the snowboard. A snowboard designed in this manner is most susceptible to plowing.
Carpenter et al. show (FIG. 1) a snowboard having thinner fore and aft sections separated by a thicker central platform having an essentially constant thickness. While a snowboard designed in accordance with the teachings of Carpenter et al. will be easier to control in turns than Remondet""s snowboard, plowing is still a substantial problem.
Nyman shows (FIG. 2) a snowboard having a single camber and an essentially constant thickness from nose to tail (it is not clear whether the constant thickness is an intended characteristic of Nyman""s snowboard, or whether it is merely the draftsman""s contribution, for the thickness of the snowboard is not mentioned in his specification). Nyman""s snowboard may be a slight improvement over Remondet and Carpenter et al., however, its center section will still remain relatively flat during turns, and therefore, is susceptible to plowing.
Deville et al. disclose a snowboard with a core having a constant thickness in which the torsional and longitudinal stiffness characteristics of the snowboard can be more precisely selected by adding reinforcing members to the surface of the snowboard in various patterns. Deville et al. teach providing less reinforcement in the central portion of the snowboard than within the boot mounting zones. This concept likely improves the turning characteristics of Deville et al.""s snowboard in relation to the prior art; however, its performance undoubtedly leaves much to be desired. In addition, adding reinforcements to the structure of a snowboard as taught by Deville et al. creates stress concentrations within the snowboard, thereby decreasing the performance of the snowboard and increasing the likelihood of structural failure. Finally, Deville et al. mention that such reinforcements could be incorporated within the xe2x80x9cbase structurexe2x80x9d of the snowboard, but do not show nor explain how this would be accomplished.
C. General Snowboard Structure
In order to better appreciate the present invention, it is believed that an explanation of general snowboard structure would be helpful.
Referring first to FIG. 1, there is illustrated a top view of a snowboard indicated generally by reference numeral 10. Snowboard 10 has a nose 12, a tail 14, and a body 16 that extends between nose 12 and tail 14.
Although snowboard 10 will be described as being formed of separate regions, areas, zones, sections, portions, segments, etc. as if they are separate entities, such discussion is merely for the purpose of clarity, as snowboard 10 is, in fact, an integral structure from nose 12 to tail 14.
Body 16 generally includes a bottom surface 18 (not shown in this view), a top surface 20, a front portion 22 and a rear portion 26. Body 16 has an effective length 17 that corresponds to the portion of bottom surface 18 which contacts the snow when snowboard 10 is in use. The midpoint of body 16 is indicated generally by dashed line 19, while the midpoints of front and rear portions 22 and 26 are respectively indicated by dashed lines 23 and 27.
Top surface 20 of body 16 includes a front mounting zone 24 and a rear mounting zone 28, both generally indicated within the area of broken lines MZ. Front and rear mounting zones 24 and 28 are separated by a center section indicated generally by reference numeral 30. Front and rear mounting zones 24 and 28 are those areas in which conventional front and rear snowboard bindings (not shown) are respectively mounted when the snowboard 10 is in use. Front mounting zone 24 preferably encompasses the midpoint 23 of front portion 22, while rear mounting zone 28 preferably encompasses midpoint 27 of rear portion 28. Front and rear mounting zones 24 and 28 are located in these general areas in such a manner as to accommodate the height and snowboarding style of the range of riders for which the particular board is designed.
As is well-known in the art, snowboard 10 is typically designed to accommodate a pair of snowboard bindings mounted within front and rear mounting zones 24 and 28, each such binding adapted to secure one of the riders""boots to snowboard 10 during use. Each snowboard binding includes, generally, a boot bed to provide a stable surface for the boot to rest upon, means for securing the boot to the binding (such as straps, laces, or buckles), and means for securing the binding to top surface 20 of body 16 (none of the bindings""parts are illustrated).
The conventional method for securing each binding to snowboard 10 is to provide four rows of threaded inserts, each row preferably having 2 inserts. illustrated in FIG. 1 is a first set of four rows of threaded inserts 25, 29, 31 and 33 that are respectively transversely aligned across and embedded into top surface 20 of body 16 in front mounting zone 24. Similarly, a second set of four rows of threaded inserts 25xe2x80x2, 29xe2x80x2, 31xe2x80x2 and 33xe2x80x2 are transversely aligned across and embedded into top surface 20 in rear mounting zone 28. Two rows of inserts typically secure each snowboard binding; thus, inserts 25 and 29 may be selected by the user to secure the front binding, while inserts 29xe2x80x2 and 31xe2x80x2 may be selected to secure the rear binding. Other sets of inserts may, of course, be selected as desired.
The front and rear bindings each preferably include a plurality of mounting apertures (also not shown) adapted to mate with the inserts in each row. Typically, each binding is placed in position (with each mounting aperture being aligned with an insert), then the binding is bolted or screwed to the inserts. The distance between the rows of inserts that secure the front binding in front mounting zone 24 and the selected rows of inserts that secure the rear binding in rear mounting zone 28 is preferably selected so that the intended rider""s boots are separated by a distance approximately equal to the rider""s shoulders. For most riders, this spacing provides the most stable and comfortable riding stance.
Thus, it may be appreciated that conventionally the first and fourth rows of inserts 25 and 33 generally define the forward and rear boundaries of front mounting zone 24, while the rows of inserts 25xe2x80x2 and 33xe2x80x2 generally define the forward and rear boundaries of rear mounting zone 28. The center section 30 is located between the rows of inserts 33 and 25xe2x80x2.
While the use of threaded inserts is presently the standard means for securing bindings to snowboard 10, obviously bindings could be secured to top surface 20 of body 16 by any suitable means, such as use of adhesives, longitudinally-mounted rails, and the like. In such alternate constructions, the boundaries of front and rear mounting zones 24 and 28 would simply correspond generally to the outline of the portions of the front and rear bindings which are adjacent to top surface 20 of body 16.
FIGS. 2-5 show alternative cross-sections of a conventional snowboard 10. Each cross-section is taken along line Axe2x80x94A of FIG. 1 which traverses rear mounting zone 28. However, the conventional cross-sections shown in FIGS. 2-5 are representative of a transverse cross-section taken at any point along snowboard 10. The various elements shown in FIGS. 2-5 all exist in the prior art and are customarily used in the construction of conventional snowboards.
In the construction shown in FIG. 2, body 16 broadly comprises a central core 38 surrounded by a cover (unnumbered). The cover is conventionally of substantially uniform thickness all along the length of the snowboard. Two major components of the cover for core 38 are a base 32 and a cap 40. Base 32 is the major portion of snowboard 10 which comes in contact with the snow. Base 32 is preferably made of an ultra high molecular weight (UHMW) polyethylene, either extruded or sintered, chosen for its durability and the ease with which it glides over the surface of the snow. Flanking base 32 and bonded thereto are a pair of edges 34, preferably made of a high grade steel. Edges 34 cut into the snow when snowboard 10 is carving its turns. Bottom surface 18 of body 16 therefore comprises the flush bottom surfaces of base 32 and edges 34.
A lower structural layer 36, extending from side to side of snowboard 10, is preferably bonded in an epoxy adhesive to base 32 and edges 34. The predominant material for structural layer 36 is fiberglass cloth, although there is some use of hemp cloth, other textile materials, and even wood veneer. Fiberglass cloth is preferred and is laid up in either a triaxial, biaxial, or uniaxial direction, depending on the design required.
Structural layer 36 is also preferably bonded in an epoxy adhesive to central core 38. Snowboard cores can be formed from one or more of a wide number of different materials, however, laminated wood, foam, and fiberglass are the most commonly used. Laminated wood is preferred, but foam, wood and foam, and laminates of fiberglass cloth (not shown) are known.
In FIG. 2, core 38 is shown as composed of laminated wood wherein thin strips of wood 50 are laminated in a vertical orientation. Horizontal lamination is also employed but is somewhat less common. Laminated wood is preferred to using a single, solid piece of wood for two reasons. First, using a single piece of wood would require a much larger and therefore more expensive piece of wood. More importantly, large pieces of solid wood which do not contain defects, such as knots, are difficult if not impossible to obtain. Laminated wood provides more uniform strength and flexibility.
Cap 40 comprises an upper structural layer 42 and a top sheet 44. Cap 40 is normally bonded in an epoxy adhesive to core 38. Like lower structural layer 36, upper structural layer 42 is usually made of fiberglass cloth, although hemp cloth, other cloths, and wood veneer are also known. Top sheet 44 is typically a polyester sheet which functions as a canvas on which the snowboard""s graphics are displayed. Cap 40 is smoothly adhered to core 38 with outwardly extending extremities 46 of upper layer 42 being bonded to edges 48 of lower layer 36 to form the cover which seals central core 38 and provides aesthetic protection for body 16.
In FIG. 3, core 38 is made of foam 52. Core 38 can be manufactured as a solid, prefabricated foam block, or it can be the result of injecting a foaming material into a pocket formed by top layer 42 and lower layer 36. Foam is typically less expensive and more durable than wood, but usually is slightly heavier and more damp.
FIG. 4 shows a combination of wooden strips 50 formed over a centrally located layer of foam 51 to form core 38.
FIG. 5 shows a core 38 formed of wood, as in FIG. 2, the difference being that in FIG. 6 core 38 is encased within a sheath of fiberglass cloth 52. Although sheath 52 could be used in combination with any of the core constructions shown in FIGS. 2-4, it is most commonly used with a wood core.
As explained above, skis and snowboards are very structurally similar, As will be described in greater detail herein, the method of the present invention is equally applicable to skis. Therefore, a brief explanation of the general structure of a ski is also believed to be helpful.
Referring to FIG. 24, there is illustrated a side view of a ski 310 located in a snow surface 5. As is conventional, ski 310 includes a nose 312, a tail 314, and a body 316 which extends between nose 312 and tail 314. Body 316 generally includes a top surface 320, a bottom surface 318, and a mounting zone 324 located on top surface 320. FIGS. 2-5 are representative of several embodiments of a cross-section of ski 310 taken anywhere along body 316.
It is therefore a primary object of this invention to provide a method of making a snowboard or a ski that has greatly improved turning characteristics by taking into account the dynamic flexibility of the snowboard or ski along its length when downward loading increases beyond the point at which the riding edge of the snowboard or ski fully contacts the snow.
Another object of the present invention is to provide a snowboard, and a method of making same, in which the front and rear portions of the snowboard follow a single track during turns.
It is another object of the present invention to provide a snowboard that minimizes friction or drag on the snowboard as it moves through the snow, particularly during turns.
It is another object of the present invention to provide a snowboard that is easier for the rider to control during turns, especially tight, sharp turns.
The foregoing and other objects are attained in accordance with one aspect of the present invention by providing a method of making a snowboard which includes the steps of selecting a desired longitudinal curvature of the snowboard during turns, determining the desired flexibility of the snowboard at a plurality of cross-sectional portions thereof in order to achieve the desired curvature, and selecting the cross-sectional dimensions of each of the plurality of cross-sections to provide the desired flexibility.
More particularly, determining the desired flexibility of the core comprises the step of determining the desired area moments of inertia at each cross-section which, in turn, may include the step of calculating the bending moments at each cross-section. The calculation of the bending moments will require the weight and skill of the intended user of the snowboard or ski to be determined.
Calculating the bending moments at each of the plurality of cross-sectional portions also preferably includes the steps of determining the downward force exerted upon the snowboard or ski by the weight of the intended user at the plurality of cross-sectional portions, and assuming a uniform upward force exerted upon the effective length of the snowboard or ski by the surface of the snow.
In accordance with the objects of the present invention, the optimum curvature of the bottom surface of the snowboard during turns is a circular arc, however, other similar curvatures, such as parabolic, hyperbolic or elliptical arcs will produce substantial improvements in turning performance over the snowboards of the prior art.
The present invention produces a snowboard which exhibits superior control and xe2x80x9cfeelxe2x80x9d over snowboards of the prior art and substantially reduces plowing in turns, particularly tight, sharp turns. The method of the present invention may also be applied to skis.
In accordance with another aspect of the present invention, there is provided a snowboard that comprises a nose, a tail and a body formed between the nose and the tail. The body includes a bottom surface, a core, and a cover surrounding the core. Front and rear mounting zones are located on the body, and a center section extends between the mounting zones. The average cross-sectional area of the core in the center section is preferably less than the average cross-sectional area of the core in at least one of the front and rear mounting zones.
In accordance with another aspect of the present invention, the center section average cross-sectional area may be less than that in both of the mounting zones. Further, the bottom surface of the body of the snowboard is preferably capable of bowing into substantially circular arcs under ideal loading conditions. Also, the thickness of the core varies gradually between and including the mounting zones and center section. Further, the core preferably comprises a substantially homogeneous material from one mounting zone to the other.
In accordance with another aspect of the present invention, the average cross-sectional area moment of inertia of the core in the center section is preferably less than the average cross-sectional area moment of inertia of the core in at least one of the front and rear mounting zones.
In accordance with yet another aspect of the present invention, the average cross-sectional thickness of the core in the center section is preferably less than the average cross-sectional thickness of the core in at least one of the front and rear mounting zones. More particularly, in symmetrical snowboards, the average cross-sectional thickness of the core in the center section is less than that in both of the mounting zones, while in an asymmetrical snowboard, the average cross-sectional thickness of the core in the center section is less than that in only the front mounting zone.